The present invention relates to an actuator. More particularly, but not exclusively, the invention concerns an actuator for use as a pitch damper in an aircraft landing gear.
An aircraft landing gear may include pitch dampers which bias the pitch of a landing gear bogie when the aircraft is flying and the landing gear is down, and/or when the landing gear is stored in the landing gear bay. The pitch of the bogie may be such that in a multi-wheel bogie the front wheels are higher than the rear wheels, or such that the front wheels are lower than the rear wheels. Typically, such pitch dampers are part of the aircraft hydraulics system, the hydraulic system being arranged to control the pitch damper to bias the bogie appropriately.
Alternatively, pitch dampers may be independent of the aircraft hydraulics system. These pitch dampers are held in a biased position by a combination of oil and gas within the pitch damper. Any leakage of oil from the hydraulics system and/or pitch damper will affect the functioning of the pitch damper, and a small leakage may have a significant effect on the performance of the pitch damper. This leads to regular inspection of the oil level and pressure within the pitch damper, and potentially maintenance of the pitch damper, being required in order to keep the performance within acceptable parameters.
The present invention seeks to mitigate the above-mentioned problems. Alternatively or additionally, the present invention seeks to provide an improved actuator.